1. Field of the Invention
The present invention relates to a rotation detecting device that detects the rotation of a detection object on the basis of the rotation of a rotor. The rotation detecting device is suitably used in, for example, a wheel speed sensor.
2. Description of the Related Art
Ordinarily, a molded IC is used in such a rotation detecting device. The molded IC comprises, for example, a sensing element, a signal processing circuit for processing an output signal from the sensing element, and the like. The molded IC is fixed on a sensor body by covering the molded IC with resin.
In the foregoing conventional rotation detecting device, resin molding is carried out in such a manner as to cover the molded IC with resin, to integrally form the sensor body with the molded IC. In this case, a large stress is applied from the resin to an IC chip during resin molding. Thus, when stress is unevenly applied from the resin to the molded IC, and a large stress is applied to a part of the molded IC, there is a possibility that the molded IC may become broken.
Also, from the viewpoint of accuracy in rotation detection, it is preferable that the gap between a detection surface and a rotor, which is called the air gap, is as small as possible. However, since the whole surface of the molded IC is covered with resin, it is impossible to make the air gap shorter (smaller) than the thickness of the covering resin.